Population Structure, Seasonal Movements and Feeding of Queen Conch, Strombus Gigas, in Deep-water Habitats of the Bahamas

Population structure, seasonal movement, and feeding ecology were examined for an 18m-deep, unfished population of queen conch (Strombus gigas) in the southern Exuma Cays, Bahamas, More than 99% of the conch at the study site were sexually mature. Shell lip-thickness data showed that the average age was at least 6 years; however, growth in thickness between 1988 and 1991 indicated that thickness is not a satisfactory means of aging conch once erosion of the shell begins. A 4-year survey suggested that population size was relatively constant, despite advanced age of the conch. Tag-recapture data indicated highest abundance of conch in July as a result of immigration from surrounding hard-ground feeding areas in May and June, and emigration in August and September. These population shifts were corroborated by survey data and by movements of individual conch. Densities of queen conch on hard-ground mounds and in coral rubble habitats were highest in winter. Movement to sand habitat in spring was correlated with increasing bottom-water temperature until the period of maximum reproductive activity and highest density on sand in July. Little feeding occurred in the sand habitat. Return to hard-ground and rubble occurred before a decline in water temperature. There was a significant inverse relationship between density of conch on winter hard-ground habitats and photoperiod length.